The drilling of wells for oil and gas production conventionally employs longitudinally extending sections or so-called “strings” of drill pipe to which, at one end, is secured a drill bit of a larger diameter. After a selected portion of a wellbore has been drilled, and in some instances reamed to a larger diameter than that initially drilled with a drill bit (which in such instances is termed a “pilot” bit), the wellbore is usually lined or cased with a string or section of casing or liner. Such a casing or liner exhibits a larger diameter than the drill pipe used to drill the wellbore, and a smaller diameter than the drill bit or diameter of a reamer used to enlarge the wellbore. Conventionally, after the casing or liner string is placed in the wellbore, the casing or liner string is cemented into place to form a seal between the exterior of the casing or liner string and the wellbore wall.
Tubular strings, such as drill pipe, casing, or liner, may be surrounded by an annular space between the exterior wall of the pipe and the interior wall of the well casing or the wellbore wall. Frequently, it is desirable to seal such an annular space between upper and lower portions of the well depth or between adjacent horizontal zones of the well. The annular space may be sealed or filled with a downhole article, such as a conformable device. Conformable devices include packers, bridge plugs, sand screens, and seals. Swellable packers and bridge plugs are particularly useful for sealing an annular space because they swell (e.g., expand) upon exposure to wellbore fluids, wellbore temperatures, and the like and fill the cross-sectional area of the annular space.
However, such deformable materials are sometimes ineffectively placed and set in the wellbore and, therefore, do not operate as intended. For example, a deformable material may not substantially expand and form a complete seal between the tubular member and the wellbore wall. In other embodiments, a swellable packer may either degrade after a useful life and may not, therefore, effectively seal across the annular space. Such malfunctions may cause flow of formation fluids from different zones to undesirably mix, be produced at the surface, or both.
Other downhole tools and components are often exposed to aggressive environments that may corrode or degrade such tools and components. For example, downhole tools may be exposed to high temperatures and high pressures, acid gases (e.g., H2S, CO2), and solutions of varying composition, pH, salinity, which exposure may lead to pitting, corrosion, or degradation of the downhole tool or component. Often, a downhole tool or component may degrade unbeknownst to an operator of the wellbore.